(1) Field of the Invention
The present invention relates to a separable coupling between a male component and a female component which is used with to a tool for rotationally driving a screw or a nut.
(2) State of the Prior Art
Current couplings normally use conjugate male square drives and female square drives, defined for example by ISO standard 1174. The male square drive is generally integral with the head of the tool and can fit into the female square of a socket which, at its opposite end, has a driving profile designed for tightening or loosening screws or nuts. This socket may form part of a family of sockets associated with the dimension of the square drive in question. As an alternative, the male square may fit into the female square of other members such as an extension piece, a universal joint, etc.
The standardized dimensions of square drives correspond to sides 6.35 mm (1/4), 9.52 mm (3/8), 12.70 mm (1/2) long, etc. For a given square drive, corresponding to a given tool size, the torque is limited by the mechanical strength of the male square drive This greatly limits the range of sockets that can be used. For a given threaded member, the torque required for loosening is greater than the nominal tightening torque. This amount of torque is largely unpredictable, and this unpredictability can be caused by corrosion.
As a result, if the required torque is greater than the torque capacity of the male square drive, it becomes necessary to change the tool and to use the square drive with the next size up. This assumes that several tools and several boxes of sockets are available, and leads to the use of heavier, bulkier and more expensive tools.
Various proposals have been made for increasing the torque available for a given tool and with a specific hardness of steel. However, this usually involves the use of shapes derived from a hexagon (FR-A-1,560,270 and 2,682,727, U.S. Pat. Nos. 4,512,220, 4,361,412 and 4,930,378, EP-A-0,458,771), which exhibit the drawback of being incompatible with standardized male square drives.
In addition, the known profiles are not generally designed to be equipped satisfactorily with a locking ball acted upon by a spring (as far as the male profile is concerned) or with a recess for accommodating such a ball (in the case of the female profile).